It looks like your AO settings are too low, I would bump it to at least 3 but you might have to go to 4.
Your blurriness and shadow subdivisions are also too low, I would change those from 2 to at least 3 and see if you need to go further.
You can probably get away with changing your Error Threshold to something like 10%. That will speed up your render and you probably won’t get any additional artifacting.
I attached a screenshot of render settings that I usually start with. If I’m getting noise then I’ll take the main Sampling Subdivisions to 4 and change the blurriness subdivs and shadow subdivs to 4 as well.
See how that works.
